Field of the Invention
The present invention relates to improvements in or relating to the treatment of waste or refuse in a rotary drum, for the recovery of useful gaseous components from material which is being treated. More particularly, the present invention relates to a rotary drum or similar vessel which can be rotated, for the pyrolysis or similar thermal treatments of the material to be handled in the vessel. The vessel is associated with a collecting chamber, for heated or heating gases, which serves in the addition and in the removal of heating gases, on each end of the vessel, with the chambers being in communication by way of heated gas ducts traversing the interior of the vessel, and by way of passages in the end walls of the vessel. The assembly also includes a seal arrangement between pertaining fixed collecting chambers and the vessel. Such an arrangement is also described in German Patent No. 2,713,031.
A drum of this type serves to recover useful gas from refuse material by pyrolysis. For this, comminuted material, preferably material which has been granulated, is introduced into the gastight and indirectly heated pyrolysis drum. The gas is produced at temperatures of approximately 450.degree. to 550.degree. C. under the exclusion of oxygen, and the gas is separated from the residues, such as ashes and other small particles. The gas, hereinafter generally referred to as pyrolysis gas, is further treated in other processing sequences, such that it can be used, for example, in the provision of power in gas turbines and gas motors or engines. As well, such gas can be used in chemical industries as synthesis gas for new products, for utilization of contained heat values, as by-pass for boiler installations, or for the operation of block-heating power plants. Treatment of the pyrolysis gas is usually carried out at a cracking temperature of 1100.degree. to 1200.degree. C. Long chain carbohydrates are converted to methane and hydrogen and other simple carbohydrates under such conditions.
Heating of the drum is achieved in an indirect manner, for example, by way of gas burners or oil burners, whereby the heating gases of one heating gas collecting chamber on the one end face are passed to the drum, and are passed from there, through passages or bores, into the heating gas conduits or tubes, which tubes extend through the interior of the drum. On the other side the cooled heating gases which emanate from the tubes are collected again in a heating gas collecting chamber, from where they are removed for a renewed heating, and are subsequently passed again into the heating gas collecting chamber at the other side or end of the drum.
A problem arises with the drum when sealing it with respect to the atmosphere, and with respect to the heating gas collecting chambers, respectively. Due to the relatively rough operation and inaccuracies of tolerances, the seals are subjected to high demands, or such seals have a short durability or life span. When heated gases or air enter through such inefficient seals into the interior of the drum, this will lead to considerable reduction of the efficiency losses of the overall processing.
In addition, the high temperature differences lead to problems with respect to the sealing and various material expansions.